[AstroPy] Doubt regard astroquery.gaia

[Adrian Price-Whelan]

Hi Abhijeet,

The returned stars are within a separation of 1 degree: the fact that they
span a larger range of longitude (RA) values is because at a given latitude
(Dec), an angular displacement is ∆ø=∆RA cos(Dec), so here:

∆RA ~ 2º @ Dec = 60.75º
∆ø ~ 2º * cos(60.75*pi/180) ~= 2º * 0.5 ~ 1º

best,
Adrian

On Thu, May 13, 2021 at 8:53 AM Abhijeet Patil <
abhijeet.patil at xaviers.edu.in> wrote:

> Respected members of Astropy community,
>
> I am Abhijeet Patil, an MSc Physics student of St. Xaviers College,
> Mumbai, India. In my final semester I am working on an astronomy related
> project and I am extensively using the astropy package. I must mention that
> the developers have done a great job in making the software. It is a very
> useful package.
>
> I want to point out that, when I downloaded the GAIA data using the
> astroquery.gaia module with radius of 1 degree data around the center of
> NGC 2516, the plot of RA and DEC shows a different span for RA values. That
> is, from the center of RA (119.5 degree), the data spans till 121.5 deg;
> two times the radius selected. There is no problem for the DEC value.
>
> I tried with data encompassing stars within 2 degree and 5 degree from the
> center of NGC 2516. But the same problem persists.
>
> Can you please provide a proper explanation for this?
>
> I would be glad if you correct me.
>
> For your reference, I have attached the respective files.
>
> Thank you for your kind attention.
>
> Regards
> Abhijeet
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>


-- 
Adrian M. Price-Whelan
Flatiron Institute, NYC
http://adrn.github.io
(he / him)
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